Combination of active ingredients for inhibiting or controlling ammonia nitrification in arable topsoil and subsoil

ABSTRACT

This patent describes nitrification inhibitors characterized by the fact that they contain as their active ingredients a substituted pyrazole, or a salt or metallic complex thereof, dicyanodiamide, and one of the compounds 
     ammonium thiosulfate, 
     biguanide, or 
     ammonium rhodanide. The combinations of the present invention are more efficacious than the individual ingredients alone and binary combinations of the same ingredients, and are thus superior to same from the ecological, phytotoxicity, and cost-effectiveness stand-points, as well as in terms of their tendencies to form undesirable residues.

BACKGROUND OF THE INVENTION

This application is a 371 of PCT/DE95/00243 filed Feb. 20, 1995.

The present invention concerns combinations of active ingredients for inhibiting or controlling nitrification of ammonia in arable topsoil and subsoil. It is known that ammonia and ammonium compounds in soil are rapidly oxidized by bacterial action to form nitrites in intermediate stages, and ultimately to nitrates. Nitrate ions cannot be sorbed by the sorbing agents present in soil, and may thus be washed out, and cause eutrophication of ground water and surface runoff.

On the other hand, high concentrations of nitrites and nitrates in soil frequently lead to toxicologically questionable levels of nitrate enrichment in plants. Moreover, denitrification (chemical and bacterial reduction of nitrates in soil), particularly under anaerobic conditions, depletes nitrogen by reducing nitrates formed by nitrification processes to gaseous nitrogen compounds, largely nitrous oxide, which then escape and pollute the atmosphere.

It is also known that certain chemicals inhibit bacterial oxidation. For example, it has been proposed that substituted pyrazoles (U.S. Pat. No. 3,494,757, DD 133088), their salts (U.S. Pat. No. 367,735,690, JP 7247182), and other compounds, such as dicyanodiamide (DE 2702284, DE 2714601), guanyl thiocarbamide (JP 7301138), nitrapyrine (U.S. 3,424,754, SU 1085966), and thiadiazole (JP 730704, JP 7204964) be employed as nitrification inhibitors.

Combinations of active ingredients, such as pyrazole and dicyanodiamide (DD 222471), pyrazole and guanyl thiocarbamide (DD 247894), and dicyanodiamide and ammonium thiosulfate (DE 3714729), are known to inhibit nitrification.

These known compounds and combinations suffer from various types of problems. For some, the problem is their efficacies are too low or that the required dosages are extremely large, which may often lead to phytotoxicity occurring in cultivated plants, or to problems with residues in plants, particularly those having short vegetative cycles. High volatilities and low migration rates are frequently the cause of low efficacies and high levels of environmental pollution.

SUMMARY OF THE INVENTION

The object of the present invention is identifying new combinations of active ingredients that do not suffer from these problems. In particular, the combinations of the present invention should be more effective and less expensive, and should have better behaviors in relation to residues and effectively eliminate phytotoxicity effects, due to dosages being much lower than if their active ingredients were employed alone.

Surprisingly, it has been found that combinations containing as their active ingredients

a) at least one substituted pyrazole (P), or a salt or metallic complex thereof,

b) dicyanodiamide (DCD), plus

c) at least one of the compounds (X)

ammonium thiosulfate,

biguanide, or

ammonium rhodanide,

give rise to strong synergetic effects on nitrification in amble topsoil and subsoil when applied jointly, and produce much better results than binary combinations of the same active ingredients (cf. Table 8), which, in turn, result in better potential utilization of the nitrogen of nitrogen fertilizers present in soil by plants, as well as better biomass yields.

The combinations of the present invention are ecologically superior and more cost effective.

They may be employed in mixing ratios ranging from 99:1 to 1:99 (DCD:X) and 75:1 to 1:1 (DCD+X):P!.

They are preferentially applied in the form of suitably formulated solutions, suspensions, sprayable powders, or emulsion concentrates, either alone or in conjunction with solid or liquid, mineral or organic, amide and/or ammonia, fertilizers.

The combinations of the present invention may be applied prior to, along with, or subsequent to, fertilizers, and may or may not be applied in conjunction with other agrochemicals, such as herbicides, pesticides, growth regulators, or soft improvers, or with other agricultural measures.

PREFERRED EMBODIMENTS OF THE INVENTION

The following examples will serve to clarify the present invention, but shall not be construed as delimiting or imposing any restrictions on same.

EXAMPLES

The efficacies of the ternary combinations of active ingredients of the present invention were investigated in a series of model studies conducted on soil samples and compared with results obtained for binary combinations of the same ingredients.

Analytical Procedures Employed for Quantifying Nitrification-Inhibition Efficacies

Sets of 100 g samples of air-dried soil (sandy loam with a pH of 6.1, an organic content of 1.19%, and a T of 5.0 mval/100 g of soil) that had been passed through a 2-mm sieve were prepared by adding 10 mg of nitrogen in the form of ammonium sulfate and the various proportions of active ingredients. The samples were then thoroughly mixed, brought up to 50% of their moisture-retention capacities, and transferred to 250-ml plastic bottles, which were sealed with thin polyethylene foil and incubated in an air-conditioned darkroom at temperatures of 20° C.±2° C.

Samples for analysis, consisting of 5.75 g of soil (5 g air-dried weight), were withdrawn at intervals of seven days and their nitrogen contents extracted by adding 50 ml of a normal solution of KCl and then shaking them for one hour in an overhead shaker. The resultant extracts were suitably prepared and their nitrogen (NH₄ and NO₃) contents determined using an ADM 300 automatic analyzer.

Percentage nitrification inhibitions were then computed from the relation ##EQU1## where K is the nitrate concentration in soil samples admixed with nitrogen fertilizer, but no active ingredients,

A is the nitrate concentration in soil samples admixed with both nitrogen fertilizer and active ingredients, and

B is the nitrate concentration in soil samples that had no nitrogen fertilizer or active ingredients added.

Concentrations and Mixing Ratios Employed

Total concentrations of the active ingredients of the present invention were 3 ppm in all cases. Mixing ratios (DCD+X):pyrazole derivative! were held constant at 25:1 while DCD:X proportionings were 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, and 1:4, yielding the following partial concentrations for the active ingredients involved:

                  TABLE 1                                                          ______________________________________                                         Ternary combinations                                                           Mixing-Ratio                                                                            DCD:X                     Total Con-                                  Numerical                                                                               Mixing   Partial Concentrations  ppm!                                                                    centration                                  Code     Ratio    DCD     X      P      ppm!                                   ______________________________________                                         1        4:1      2.308   0.577  0.115 3                                       2        3:1      2.163   0.721  0.115 3                                       3        2:1      1.923   0.962  0.115 3                                       4        1:1      1.442   1.442  0.115 3                                       5        1:2      0.962   1.923  0.115 3                                       6        1:3      0.721   2.163  0.115 3                                       7        1:4      0.577   2.308  0.115 3                                       ______________________________________                                    

                  TABLE 2                                                          ______________________________________                                         Binary combinations                                                            All binary combinations had a DCD:X mixing ratio of 1:1. The other             mixing ratios involved were the same as those employed for the ternary         combinations of the present invention                                                                           Total                                         Mixing-Ratio       Partial Concentration                                                                        Concentration                                 Code Symbol                                                                             Combination                                                                               ppm!          ppm!                                         ______________________________________                                         4/1      DCD + X   1.442 ± 1.442                                                                             2.884                                         4/2      DCD + P   1.442 ± 0.115                                                                             1.557                                         4/3      X + P     1.442 ± 0.115                                                                             1.557                                         ______________________________________                                    

                  TABLE 3                                                          ______________________________________                                         List of active ingredients investigated                                        Designation/Chemical Formula                                                                              Symbol                                              ______________________________________                                         Dicyanodiamide             DCD                                                 Guanyl thiocarbamide       GTH                                                 Thiocarbamide              TH                                                  Ammoniuim thiosulfate      ATS                                                 Ammonium rhodanide         AR                                                  3-methylpyrazole           MP                                                  1-guanyl-3-methylpyrazole x HNO.sub.3                                                                     GMP x NO.sub.3                                       Mn(MP).sub.2 !(H.sub.2 O)!Cl.sub.2 manganochloro-methylpyrazole                                          Mn/MP                                               complex                                                                        ______________________________________                                    

Computation and Analysis of the Efficacies of the Combinations Studied

The efficacies of the combinations studied were computed using the technique of Colby (Weeds 15 (1967), pp. 20-22), which is based on efficacy complements, E', given by

    E'=100-E,

where E are the respective efficacies, expressed as percentages. ps Theoretical values of these complements for those combinations whose efficacies, E, are purely additive were computed from the relation ##EQU2## where x₁ is the value of E' for compound A, present in concentration C_(A),

y₁ is the value of E' for compound B, present in concentration C_(B),

z₁ is the value of E' for compound C, present in concentration C_(C),

n is the total number of active ingredients present in the combination, and

E_(T) is E'_(true), the empirically determined value or E' for the combination involved.

The results of combining ingredients were categorized as follows:

E>E_(T) implies that there is synergism among the active ingredients,

E<E_(T) implies that the active ingredients counteract one another, and

E=E_(T) implies that the efficacies of individual active ingredients are purely additive.

In order to simplify quantifying the results of employing combinations of active ingredients, we computed efficacy factors, EF, given by ##EQU3## where EF>1 implies that there is synergism among the active ingredients,

EF<1 implies that the active ingredients counteract one another, and

EF=1 implies that the efficacies of individual active ingredients are purely additive,

E_(true) =100-E_(T), and

E_(theor) =100-E.

Efficacies of Individual Active Ingredients

The efficacies of individual active ingredients were determined from linear regressions applied to sets of four empirically determined data points for the concentration ranges

0.5 ppm-2.5 ppm for DCD and X, and

0.075 ppm-0.5 ppm for the pyrazoles studied.

In the interest of simplicity and clarity, the tables below list only the regression relations and data points employed in computing the efficacies for the various individual active ingredients.

                  TABLE 4                                                          ______________________________________                                         Active Ingredient  Regression Relation                                         ______________________________________                                         DCD                y = 5.83 x + 20.44                                          GTH                y = 10 x - 4.1                                              TH                 No effects were discernible                                 ATS                28 days after application                                   AR                 of the concentrations employed.                             MP                 y = 162.6 x + 17.6                                          GMP x NO.sub.3     y = 38.1 x + 26.7                                           Mn/MP              y = 81.7 x + 17.7                                           ______________________________________                                    

                  TABLE 5                                                          ______________________________________                                         Active   Percentage Nitrification Inhibition After 28 Days                     Ingredient                                                                              0.115  0.577  0.721                                                                               0.962                                                                               1.442                                                                               1.923                                                                               2.163                                                                               2.308                          ______________________________________                                         DCD      --     23.8   24.6 26.0 28.8 31.7 33.1 33.9                           GTH      --     1.7    3.1  5.5  10.3 15.1 17.5 19.0                           TH       --     0      0    0    0    0    0    0                              ATS      --     0      0    0    0    0    0    0                              AR       --     0      0    0    0    0    0    0                              MP       36.3   --     --   --   --   --   --   --                             GMP x NO.sub.3                                                                          31.1   --     --   --   --   --   --   --                             Mn/MP    27.1   --     --   --   --   --   --   --                             ______________________________________                                    

                  TABLE 6                                                          ______________________________________                                         Efficacies of binary combinations 28 days after application                                  E.sub.true                                                       Combination    %     E         E.sub.T                                                                             EF                                         ______________________________________                                         DCD + GTH     39.2   63.9      60.8 1.09                                       DCD + TH      30.0   71.2      70.0 1.04                                       DCD + ATS     29.1   71.2      70.9 1.01                                       DCD + AR      26.4   71.2      73.6 0.92                                       DCD + MP      69.4   45.4      30.6 1.27                                       DCD + GMP x NO.sub.3                                                                         67.3   49.1      32.7 1.32                                       DCD + Mn/MP   62.4   51.9      37.6 1.30                                       GTH + MP      48.1   57.1      51.9 1.12                                       GTH + GMP x NO.sub.3                                                                         45.8   61.8      54.2 1.20                                       GTH + Mn/MP   37.9   65.4      62.1 1.10                                       TH + MP       31.9   63.7      68.1 0.88                                       ATS + MP      34.7   63.7      65.3 0.96                                       AR + MP       35.2   63.7      64.8 0.97                                       ______________________________________                                    

                  TABLE 7                                                          ______________________________________                                         Efficacies of combinations of active ingredients of the                        present invention                                                                         DCD:X       E.sub.true                                              Combination                                                                               Mixing Ratio                                                                                %!    E     E.sub.T                                                                             EF                                    ______________________________________                                         DCD + GTH + MP                                                                            1           79.9   41.4  20.1 1.36                                             2           84.3   41.3  15.7 1.44                                             3           82.8   41.1  17.2 1.41                                             4           92.1   40.7  7.9  1.55                                             5           79.0   40.0  21.0 1.32                                             6           78.6   39.6  21.4 1.30                                             7           70.3   39.3  29.7 1.16                                  DCD + TH + MP                                                                             1           86.2   42.1  13.8 1.49                                             2           85.0   42.6  15.0 1.48                                             3           80.2   43.5  19.8 1.42                                             4           78.0   45.4  22.0 1.43                                             5           72.4   47.1  27.6 1.37                                             6           67.9   48.0  32.1 1.31                                             7           58.4   48.5  41.6 1.13                                  DCD + ATS + MP                                                                            1           95.6   42.1  4.4  1.65                                             2           95.5   42.6  4.5  1.66                                             3           95.5   43.5  4.5  1.69                                             4           94.1   45.4  5.9  1.72                                             5           90.9   47.1  9.1  1.72                                             6           83.1   48.0  16.9 1.60                                             7           72.2   48.5  27.8 1.40                                  DCD + AR + MP                                                                             1           86.5   42.1  13.5 1.49                                             2           84.0   42.6  16.0 1.46                                             3           84.5   43.5  15.5 1.50                                             4           90.1   45.4  9.9  1.65                                             5           72.6   47.1  27.4 1.37                                             6           67.9   48.0  32.1 1.31                                             7           49.2   48.5  50.8 0.96                                  DCD + GTH +                                                                               1           93.7   44.8  6.3  1.70                                  GMP x NO.sub.3                                                                            2           90.3   44.7  9.7  1.63                                             3           91.5   44.5  8.5  1.65                                             4           97.0   44.0  3.0  2.20                                             5           83.3   43.3  16.7 1.47                                             6           79.8   42.9  20.2 1.40                                             7           75.1   42.5  24.9 1.31                                  DCD + GTH +                                                                               1           82.4   47.4  17.6 1.57                                  Mn/MP      2           83.5   47.3  16.5 1.58                                             3           78.2   47.1  21.8 1.48                                             4           75.1   46.6  24.9 1.41                                             5           70.0   45.8  30.0 1.29                                             6           58.4   45.3  41.6 1.07                                             7           50.3   45.0  49.7 0.91                                  ______________________________________                                    

Table 8, below, presents evidence that the multicomponent combinations of the present invention are superior to binary combinations of the same active ingredients.

                  TABLE 8                                                          ______________________________________                                         A comparison of the efficacies of combinations of the present invention        with those of binary combinations of the same active ingredients               Combination        Mixing Ratio                                                                              EF                                               ______________________________________                                         DCD + GTH + MP     4          1.55                                             DCD + GTH          4/1        1.09                                             DCD + MP           4/2        1.27                                             GTH + MP           4/3        1.12                                             DCD + TH + MP      4          1.43                                             DCD + TH           4/1        1.04                                             DCD + MP           4/2        1.27                                             TH + MP            4/3        0.88                                             DCD + ATS + MP     4          1.72                                             DCD + ATS          4/1        1.01                                             DCD + MP           4/2        1.27                                             ATS + MP           4/3        0.96                                             DCD + AR + MP      4          1.65                                             DCD + AR           4/1        0.92                                             DCD + MP           4/2        1.27                                             AR + MP            4/3        0.97                                             DCD + GTH + GMP x NO.sub.3                                                                        4          2.20                                             DCD + GTH          4/1        1.08                                             DCD + GMP x NO.sub.3                                                                              4/2        1.32                                             GTH + GMP x NO.sub.3                                                                              4/3        1.20                                             DCD + GTH + Mn/MP  4          1.41                                             DCD + GTH          4/1        1.08                                             DCD + GMP x NO.sub.3                                                                              4/2        1.32                                             GTH + GMP x NO.sub.3                                                                              4/3        1.20                                             ______________________________________                                     

We claim:
 1. A composition for use in inhibiting and controlling the nitrification of ammonium nitrogen in arable soils and substrates, said composition comprising:a first compound selected from the group consisting of substituted pyrazole, its salt and metallic complex thereof; a second compound represented by dicyanodiamide; and a third compound selected from the group consisting of ammonium thiosulfate, biguanide and ammonium rhodanide,wherein the mixing ratio of the second compound to the third compound ranges from 4:1 to 1:4 and the mixing ratio of a combination of the second and third compounds to the first compound ranges from 35:1 to 5:1.
 2. A method of inhibiting and controlling the nitrification of ammonium nitrogen in arable soils and substrates, comprising the step of applying to the soil an amount effective therefor of a composition including a first compound selected from the group consisting of substituted pyrazole, its salt and metallic complex thereof, a second compound represented by dicyanodiamide; and a third compound selected from the group consisting of ammonium thiosulfate, biguanide and ammonium rhodanide, wherein the mixing ratio of the second compound to the third compound ranges from 4:1 to 1:4 and the mixing ratio of a combination of the second and third compounds to the first compound ranges from 35:1 to 5:1.
 3. The method of claim 2 wherein the composition is applied in the form of a solution, suspension, wettable powder or emulsion concentrate at a dosage of at least 1 kg of active ingredient per hectare.
 4. The method of claim 2 wherein the applying step includes combining the composition with solid and liquid mineral and organic fertilizers selected from the group consisting of amide-containing fertilizers and ammonium-containing fertilizers for application.
 5. The method of claim 2 wherein the applying step includes combining the composition with an agrochemical selected from the group consisting of herbicides, pesticides, growth regulators and soil-enrichment agents.
 6. The method of claim 2, wherein the composition is applied with an amount of at least 0.5% related nitrogen content of a nitrogen containing mineral fertilizer. 